aragonite after calcite (?)

A porous (low density), cryptocrystalline mass of ivory-white aragonite, coralloid in form and with a chalky lustre. Close examination shows relict crystal outlines indicating the aragonite is pseudomorphous after a rhombohedral carbonate – probably calcite (?).

ESD analysis (Frank Keutsch, Harvard University, 2025) indictates that the aragonite contains circa 5 wt % Pb and essentially no Zn.

The specimen was number 602 in the collection of Wilhelm Klein, production manager at Tsumeb between 1916 and 1939. His handwritten catalogue attributes the specimen to 11 Level in the first oxidation zone.